The invention relates to an anode-side actuated semiconductor component, for which the semiconductor element has a plurality of side-by-side arranged, parallel connected unit cells with thyristor structure, and to bidirectional semiconductor switches with such an anode-side actuated semiconductor component.
Bidirectional semiconductor components, which can be switched on and, if possible, also switched off by a control signal in both polarity directions of the main electrodes are highly advantageous for alternating current uses. A frequently used component of this type is the Triac, which comprises two antiparallel-arranged thyristor structures and can be switched on through gate current, independent of the polarity sign of the voltage that is present. The Triac cannot be switched off via the gate, but only through a polarity reversal of the main electrodes.
A component, which can be switched on as well as off by a MOS gate in both polarity directions was described in IEEE Transactions on Electron Devices, Vol. ED-27 (1980), pp 380-87. This so-called TRIMOS (MOS-Triac) is a lateral component, comprising two DMOS transistors in a laterally reversed arrangement, for which the gate electrodes are mutually connected. The voltage range is limited in this case by the breakdown voltage of the gate oxide and typically only extends to about 50 V. If the gate electrodes are separated and actuated individually, voltages of up to 300 V can be reached. It is favorably in this case that the component functions at higher currents like an IGBT, so that the on-resistance is reduced through conductivity modulation. However, advantages during the actuation are lost again when separating the gate electrodes.
A bilaterally switching component with thyristor structure and lateral layout, which is referred to as BEST (bilateral emitter switched thyristor), was presented at the International Electron Device Meeting IEDM 1992 (IEDM'92 Conference Volume, pp 249-252). The blocking capacity of the component was less than 70 V. The characteristics are comparable to those of the TRIMOS. Not only the voltage range, but also the switchable current is narrowly limited as a result of the lateral layout of these switching elements. A separate MOS gate is provided for switching on and switching off in each current direction, which is actuated by the cathode electrode of the respective current direction. This is a disadvantage because of the expenditure for the driver electronics. Such a concept is not suitable for vertical bidirectional components.
The standard power components such as the MOSFET, the insulated gate bipolar transistor or IGBT, the normal bipolar transistor and the (GTO) thyristor are actuated from the cathode and require a positive control voltage for the switching on. For a bidirectional switch, which referred to a (relatively small) gate signal can be switched to a fixed main electrode, an anode-side actuated components is necessary in addition to the standard cathode-side actuated component. By exchanging n- and p-conductivity type in the various semiconductor zones, anode-side actuated components are obtained from the aforementioned standard structures. However, these have the disadvantage is that they cannot be integrated together with the standard ones, among other things because the weakly doped base for absorbing the voltage has the reversed conductivity type, namely p-conductivity. A second disadvantage of this anode-side actuated component is that the gate signal must have a polarity for the switching that is the reverse of the normal one: a negative voltage at the gate is necessary for switching on. A bidirectional switch with such individual components thus requires control signals for the switching on and off, which depend on the current direction, so that the control signal changes, among other things, for the zero passage of the current. A very involved driver electronics is consequently required.
A MOS-controlled thyristor was suggested in the German Patent Application P 44 02 877, which can be switched on and off in series to the thyristor structure by a p-channel MOSFET that is integrated into the n-emitter zone. During the switching off, a voltage that builds up at the MOSFET is transmitted as a negative gate voltage to the p-base of the thyristor by a second integrated MOSFET, which switches on automatically once the first one is switched off. This permits an efficient switching off. The externally actuated MOSFET and the thyristor are integrated by using a second, internal MOSFET of the type of a known cascode circuit. The component permits a high on-state current per surface with low on-state voltage, can be used up to high blocking voltages, and has a characteristic with current limitation.
As described in this patent application, an inverse component is obtained by exchanging the n- and p-conductance in the various semiconductor zones, which can be actuated from the anode side. Like the standard components, this component is switched on by positive gate voltage and is switched off by removing or reversing the gate signal. Since it has a weakly doped p-base zone for absorbing the voltage, it is not suited to monolithic integration together with the standard components, which have a transistor or thyristor structure.